High-power VCSEL-arrays (vertical-cavity surface-emitting laser arrays) are excellent candidates for illumination applications as compared to LEDs (light-emitting diodes): The spectral width of VCSELs is narrower than that of LEDs (1-2 nm vs. a few tens of nm), and the efficiency of VCSELs is higher than that of LEDs (30% vs. 10%). In some applications, it is advantageous to diffuse the light emitted by a VCSEL.